Replaceable gun lining



3 Sheets-Sheet 1 Filed May 7, 1945 3mm/vbo@ Mal: Kta

LED

@ttm/mags April 24, 1951 MAcKTA 2,549,832

REPLACEABLE GUN LINING Filed May '7, 1945 3 Sheets-Sheet 2 LEU; MacKa.

SVM/M4113 s April 24, 1951 L. MACKTA 2,549,832

REPLACEABLE GUN LINING Filed May 7, 1945 3 sheets-sheet s L En MHCK-La 33 a wm www abtowms Patented Apr. Z4, 1951 atraen NETE@ STATE FYEN'E OFFKCE j 2,549,832 f REPLACEAELE GUN LrNrNG Leo Mackta, Brooklyn, N. Y. Application May i, 1945, serial No. 592,435

(Granted 'under the act of March 3, 1883, as amended .april 30, 1928; 370 0. G. 757) 12 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes Without the payment to me of any royalty thereon.

The invention relates to an improved gun, and to ammunition and other elements of a novel load for use therein, as well as to the means for loading the gun and firing the same.

One object of the invention is to provide means for maintaining a. gun in elective condition and particinarly in minimizing erosion, and also by enabling frequent renewal of chamber surfaces, and to provide material and present a method of effecting frequent renewal of rifling, even with each shot fired if desired, and in such event to present ammunition embodying the necessary elements for effecting such renewal incident to and as a part of the operation of loading the gun. It is an important advantage in this respect that such loading may be effected with about the same facility and time of loading as with conventional ammunition.

f `Another important aim is to present novel means for securing a rifling assembly separably in the bore of a gun tube. That is to say, it is contemplated to have a more or less simple borev in that part of the tube intended for the passage or' the proiectile and to enable the insertion or removal of my land means at will Ywithout re- ,quiring machine shop operations, and with the gun in its usual place of operation, whether in the field or in a permanent emplacement. Also it is the aim to enable such emplacement and removal by the use of such simple loading mechanism as will correspond closely to conventional li' construction and operation and readily operable without detriment to eicient and rapid ring or the weapon.

1t -is a further object of the invention to present a gun which may be used for high velocity action with artillery calibers While at the same time being readily portable. A further aim is to present the invention in a practical adaptation to use with tapered bores, particularly in reference tc the novel riing above referred to.

Erosion of the barrel of a gun begins principally at the forward part oi the chamber, and this is quickly followed by destruction of the near @"d portions of the lands in the bore and the ing cone at the throat. The destruction of part of the lands results in anV initial movement ci the projectile Without rotation, and the relatively uneroded portions of the lands are then encountered with such abruptness by the projec- Vtile sealing or rotating rings or anges, that a severe and destructive shock and tearing action is imparted to the material of the barrel and the projectile, hastening deterioration of the gun and impairing the `effective flight of the projectile. 1n addition to deviation from a true line of night, the trajectory of the projectile becomes modified at an early stage in such erosion involving uncertain rang-e, and this also seriously affects the lighting value of armament because of the uncertainty of aiming. Erosion of the lands progresses forwardly with each shot. It often is nec'- essary for artillery or other guns in critical battles to be continued much long-er in use than the maximum ordinarily expected and in some cases a projectile will move more than its length in the bore before encountering adequate land elements to effect its rotation, and the resultant shock then is a serious threat to the safety of operation of the gun, not to mention the loss of range 'and accuracy involved. It is believed that prevention of initial erosion at the forward part of the chamber will delay the erosion or the lands materially, for a numb-er of reasons which will be understood, including avoidance of focusing gases in the space enlarged -by erosion, upon the more restricted part of the bore in advance thereof.

For the last reasons as well as to enable repair or prevention of erosion of the chamber and bore, it is an aim of my invention to enable the renewal of the face of the chamber at frequent intervals,

`in a novel, economical, and simple way, which may be carried out without returning the gun to a manufacturing or base repair plant.

The desirability and diiculty of avoiding excessive heating of guns incident to battle firing is well understood and it is an object of this invention also to enable the dissipation of heat imparted to face materials of the bore and chamber at a distance from the gun so as to enable sustained and more frequent fire of large caliber guns especially.

Still further objects, advantages, and features or invention and the nature of the invention otherwise will appear from the following description and accompanying drawings, wherein:

Fig. l is a longitudinal sectional View of a gun embodying my invention with the breech sleeve or chamber wall element withdrawn, a load in the chamber and the breech sleeve positioned for return, the cartridge case-liner being in section.

Fig. 2 is a similar view with the breech sleeve in closed position, a partei the cartouche and projectile being in section.

Fig. 3 is a rear elevation of the gun with open breech.

Fig. 4 is a similar view closed.

Fig. 5 is a fragmentary longitudinal section on the line 5 5 of Fig. 3 with a cartridge unit and case in position and with the breech sleeve and obturator piston at an intermediate position in opening movement, illustrating initial action of the ejector.

Fig. 6 is a similar view with the breech fully opened. Y

Fig. 7 is a plan of the blank for the load case and barrel liner.

Fig. 8v is .a fragmentary section of a possible form of sheet material for production of the combinedr case and liner.

Fig. 9 is a fragmentary enlarged cross section y of the barrel.

Fig. 10 is a developed approximate face View of the bore and a liner therein showing a grooving of the barrel in relation to a passing sealing or rotating ring.

lFig. 11 is a similar View of another arrangement of the grooves longitudinally of the barrel.

Fig. 12 is a similar view illustrating the use of recesses of small dimensions longitudinally of the barrel or interrupted grooves.

Fig. 13 is a similar view illustrating barrel grooves coincident in direction with the lands.

There is illustrated a gun comprising a base 29 which may have any suitable mounting for pointing of the gun, these details not being illus trated, since they are not a novel feature of my invention.v On this base there is rigidly secured a barrel or tube 3l) which includes a bore 3l and a chamber, the latter comprising a chamber recess 32v formed immediately to the rear of the throat or forcing cone 33 constituting a tapered enlargement of the bore leading from the recess 32. In the present instance, for convenience in illustrating the invention, the recess 32 is continued through the breech end of the gun with a slight further recess 34 in which interrupted interior threads 35 are formed, such as those of conventional breech recesses. The forward end of the recess 32 forms a shoulder 36 at therear of the throat on the tube. The tube may be conventionally reinforced or assembled, these details not being illustrated.

For the purpose of portability the bore portion of the barrel in this instance is quite short in pro.n portion to the caliber thereof, and is formed with a pronounced taper reducing its diameter progressively from the throat to the muzzle. The tapered bore may be smooth or formed with small grooves, recesses or other irregularities of slight altitude as compared to conventional rifle lands, and not intended as riing, as will be more particularly described.

The breech closure and chamber assembly.-A revoluble closure or breech sleeve is provided, consisting of a cylindrical sleeve 3l adapted to extend into the recess 32 to or near the shoulder 36. If desired a tapered t may be employed to facilitate a supporting contact between the face of the recess and that of the sleeve. The sleeve is formed with an integral head 38, and exteriorly is provided with conventional interrupted threads 39 coordinated with those of the recess 3ft for sliding movement of the closure inwardly to near final position and then rotation to coengagethe threads. A radial operating handle QB is mounted on an extension of the closure, and isl vertical When in unlocked position.

The breech sleeve 3T is supported slidably for movement into and out of the recess 32 by means of a frame 4I rockable transversely. The frame includes a longitudinal rectilinear base shaft or bar 42 parallel to the axis of the tube, revolubly mounted in bearings d3 beneath the chamber portion of the tube and it extends rearwardly of the breech of the gun a distance at least equal to the length of the closure including the sleeve. A stop collar 42, is provided on the forward end of the bar. At the rear end of the bar e2 a lever arm 4d is fixed thereon, extending vertically upward in closed positions of the parts, and oscillatable with the bar for movement to the right as in Fig. 3, and return. The base 29 extends beneath the lever and a stop lug is formed on the lever to engage the base and limit movement of the lever toward the right as the parts are viewed in Figs. 3 and 4.

A stud sh aft 43 is xed in the lever 4A, projected forwardly and positioned on the lever so as to lie coaxial with the tube 3i) at the upright position of the lever. The head 38 is bored and engaged slidably on the shaft 46, and at the forward end of the shaft it there is mounted a piston 41 tted slidably in the sleeve 31, by which the latter is supported at its forward end. The piston has a forward face close to the plane of the breech end of the tube 30 and has a ring mechanism therein as shown in Figs. 7 and 8. The lever arm 44 is extended from its pivot and beyond the base ofthe shaft 4S to a distance slightly beyond the periphery of the breech closure, and provided with two forwardly projected lugs 43 positioned to receive therebetween the base of the operating handle 40 when the latter is drawn to Vits rearmost position as shown in Fig. 1. It is possible then to swing the closure, including the piston and the shaft 45 and lever arm 134 as a unit to the open breech'position shown in Fig. 3.

The l0acZ.-The ammunition is a cartridge unit 66 shown in Figs. l. and 2, and consists of a cartouche or envelope 61 which may be of fiber, and'may be destructible by the burning of the charge ES of propellant explosive therein. The cartouche corresponds to the ordinary cartridge case, and includes a thickened head 69 (which may be considered the head of the load or cartridge) axially in which is set a primer 'l shaped and exposed at 'il (Figs. 5 and 5) for engagement and detonation by the firing pin 49 when operated as described. The cartouche is formed with a cylindrical wall 'IG open at the forward end whereby the mouth of the envelope is formed and in this mouth there is snugly fitted the base of a projectile 'I2 of conventional construction. In this instance it is shown with an vintegral sealing or rotating ring or flange '13, immediately behind which suitable grooves 'l5 are formed in the projectile to receive the metal displaced by the forcing cone or throat and the vrifling of the bore when the projectile is red. The edge portion of the wall 14 is crimped inward into the rearmost groove of the projectile and secured so as to hold the latter securely in place during shipment and handling.

The Ziner.-The load also includes a metal combined case and barrel riing liner 'I6 (which may be termed a liner), surrounding the cartouche and laid snugly thereagainst. The caseliner is formed of metal which may be produced from suitable blanks by extrusion after the manner of making metal cartridge cases, or may be stamped from flat sheet stock as in Fig. 7, and

'shaped to the diameter desired. The caseV T5 5 includes a rear base flange portion 11 at right anglesV to the axis of the load and there are formed in the forward part a multiplicity of slots 'is which in the present instance open through the forward end of the liner and extend obliquely rearwardly nearly or quite to the flange portion El; in the present instance stopping short of the flange and thus leaving a circumferentially continuous throat portion 19. The material between the slots constitutes a number of lands 8B. The lands are preferably of nearly or quite uniform width from their bases at the throat portion forwardly although they may be tapered slightly toward their forward ends to maintain an intimate engagement with the sealing and rotating bands of projectiles during firing. The case-liner of the load is shown as extending slightly forward beyond the forward-most seal ing ange T3, but this length may be varied as found desirable. Also the length of the liner is in this instance slightly greater than the interior length of the recess 32. The major diameter of the lineriiange 'il is sufficiently less than that of the chamber recess 32 at the shoulder St to permit the'flange Il to lie separably against the shoulder 35i as will be made clear hereinafter. Theferward-most flange 'i3 is spaced from the rear-face of the cartouche head 69 less than the interior length of the sleeve Sl, so that when the load is positioned as in 1Eigs. l and 2 there is a clearance between the ogive, bourrelet and flange 'S3 of the projectile on the one hand, and the throat 33 and super-posed lands, on the other hand, to free the latter for forward slid* ing movement as will appear. tion between the projectile and lands the latter may be faced electrolytically or otherwise with a material 82 (Fig. 8) having a relatively low index of friction, such as copper. The body of the lands may be of a material of a hardness and toughness correlated to the material in the rotatv ing bands or ange of the projectile, and if practicable may itself have a low index of friction, so that application of the facing 32 may be dispensed with. rihis land construction may include a body of a thickness related to the material of the rotating rings or flanges, and in the wid-th of the lands. the power of the propelling charge and the safety factors in the materials of the tube and jacketing, all of which may be r calculated. It is believed that by reason of frequent replacement and consequent perfection of the driving edges of the lands, a thickness less than the depth of conventional rifling is practicable and -the width of the lands may be determined by conventional calculation modified by expediency or requirements indicated in practice. A compensating factor is the taper of the bore 3|.v Landtube keying-In case of need I have here presented in Figures 9 to 13 means to hold the lands to the bore so that relative rotation of the liner unit will not occur, notwithstandingy that "trusicn thereinto under the pressure exerted on the lands by sealing vand rotating rings, bands or flanges or projectiles, while the latter are being nropeiled by the products of combustion `of the Imopelling charges detonated in the chamber of the gun. These recesses may be termed key To minimize fric- 'f grooves or recesses. In the forms shown itis contemplated that these shall be of slight depth, only a fraction of the height of theland. As shown in Figures 9 and 10 these consist of spiral grooves or riingwhich may be continuous from the throat to the muzzle of the tube and having a direction opposite that of the direction of twist of the lands 80. An approximateshowing of the grooves 83 in cross section in Figure 9 may be modied as to size and spacing as found'desirable. The grooves 83, however, preferably have a radial side at the left as in rifling and it is thought the opposite side may simply slope as indicated. The twist or pitch of the grooves 83 may be such that theportion or any one groove exposed between two lands will be included within the longitudinal measurement of a passing sealing band or flange, as indicated in dotted lines at I3 in Fig. 10, so that leakage of gases through the grooves will be prevented.

In 'Figure ll'the key grooves E3 extend longi tudinally of the tube rectilinearly and parallel to longitudinal geometrical elements of the tube face.

In Figure 12 the key recesses Stare shown as non-continuous in any direction but vbeing slightly elongated. If this elongation is longitudinalasshown'jthe lengths of the recesses may be less than the longitudinal dimension of the rotating and sealing band 13.

In Fig. 13 the key grooves 35 shown in the bore are spiral with the same direction and pitch or twist as the lands 8S and alined therewith. A'relatively hardl resilient material in the land 'will besprung vor `deforined overthe recesses to a degree, by a passing projectile and the liner 'i6 will thereby be held against relative movement upon the face of the bore, and after the passage of the projectile will recover from such deformation so that it may he readilyv drawn from the tube.

In order to effect keying 'engagement between the land and tube by 'a somewhat different function of the land, I have' shown in Fig. 8 on the external face of the land next to the face of the bore a substantial body of `metal or other material 86 more or less plastic or owing under the high pressures involved in the passage of the rotating band or flange of a projectile through the gun. The material 88 is, united with the land body material 8l. The latter may be Ia relatively hard steel, 'while the key material may be soft iron, bronze, brass, or copper appliedin conventional ways, as for instance', by electrolytic deposition. Suchrmaterials are capable of extrusion from their initial surface contours on the lands, into the grooves or recesses, by a flowing action under the pressures indicated, yet' by alloy or otherwise may be made tough and vsuniciently resistant to shear to hold the land keyed to the tube, against the torsional forces exertedby the projectile.

The Zin-er extractor (Figs. 1, 2 cmd 3) .--A narrow longitudinal channel 83 is formed with inthe tube 3! at the lower side of the chamber .f

ment 89 on the gunfand also through the breech face 95 of thegun tube. Laid slidably in the channel. and eoextensive in length therewith there is 'a push rod 9i, at the' rear end of which lthere iswan extractor jaw @2, arranged transversely in the (chambery recess and adapted to receive the `flange il thereagainst while the jaw 92 is at initial loading position in the extreme rear part of the breech recess. The jaw 92 is adapted to support the load initially, and after positioning of the load in final position before closing of the breech will support the rear end of the load. The rod 9| has on its forward part a downwardly extended rigid arm 93 and connected revolubly to the extremity of the latter there is a draw rod 94, extended slidably through the bar 42 to a point immediately to the rear of the head 38 of the chamber member 31. From a point in advance of this the bar 42 is channelled rearwardly on its upper side to the lever arm 44, and an upstanding arm 95 is fixed on the rod 94 extending upwardly through this channel close .behind the head 38 of the breech closure or chamber member. The arm 95 is thus movable by the chamber member rearwardly carrying the push rod and ejector jaw to the positions of Fig. l.

The liner ejector (Figures and 6).-At the right of the tube and mounted thereon at and forwardly of the breech face, there is an ejector device operative to push the ange 11 of the rifling unit or liner a distance rearwardly of the breech on movement of the piston 41 and sleeve 31 to full open position. For this a housing |2| is provided on the gun adjacent a radius of the breech axis extending downwardly at an angle of approximately 45 degrees to the vertical. From the housing a slot |22 is formed through the wall of the breech recess and opening through the breech face 90 of the gun. On a pintle |23 fixed across the housing at right angles to said radius on ejector arm or lever |24 is pivoted having a length suicient to swing from a forward retracted position in the housing clear of the chamber recess, thence rearwardly through the slot |22 (Fig. 5) into the chamber but short of the lands or liner and rearwardly to the ange 11 when in initial loaded position, and beyond, as in Fig. '6. On the same pintle there is pivoted close beside the lever |24 a separate actuating lever |25 having a rearward arm |26 with an open breech position at the right hand or outer limit of its movement forwardly of the path of the piston 41 and sleeve 31 as in Fig. 6 and movable rearwardly into such path and toward the left a distance where it is checked in an initial closed breech position in such path, by its integral forwardly extended arm |21, which engages the wall of the housing to limit movement of the lever (Fig. 5). A torsion spring |28 has one end connected to the lever |25 and its other end connected to the arm |24 under stress tending to move the arms |24 and |26 toward each other. This constitutes a resilient operative connection between the arms |25 and |24.

The arm |24 is moved to its forward position by entry of the sleeve 31 into the chamber recess 32 and is so held until the sleeve is withdrawn. Outward movement of the arm |24 is limited by the end of the sleeve 31 and the piston 41. The arm |24 is so shaped that when the end of the sleeve 31 is at its full open position just out of line longitudinally with the'wall of the chamber recess, the sleeve 31 holds the arm |24 in an inoperative position a short distance rearward of the face 93. The end of the arm has an ejector bill |29 set forwardly sufficiently to lap the flange 11 when the sleeve is in loaded position or part way, inward of the face 9U of the gun. A cam |313v is' thus formed, the rear side of which engages the sleeve 31 and piston 41 to hold the bill |29 in-operative close before the ange 11. As

may be understood, the sleeve is movable laterally on opening of the breech to clear the arm |24 further and permit its full ejector action. For this purpose the arm |24 may be curved and recessed as shown to permit a good full ejection movement, and affording the rear cam face |30 against which the sleeve 31 may engage with a minimum impedance, to move the arm |214 forwardly by the lateral return movement of the sleeve 31 toward closed position, and permitting the sleeve to subsequently push the flange 11 and arm |24 forward in the sliding movement of the sleeve and liner. Y In the opening of the breech, after the sleeve 31 is fully withdrawn, in its lateral movement toward the position shown in Fig. 3, the sleeve 31 engages the arm |26 as shown in Fig. 5, at which time the arm- |24 may be at the position illustrated in full lines in Fig. 5, by reason of the spring |28 being free of strain although the arm |24l may be held by the spring further rearward and the spring may tend to hold it much further rearward. Upon engagement of the arm |26 by the sleeve 31, this arm is moved to the right, placing the spring |28 under maximum tension when the forward face portions of the closure engage against the arm |26. As soon as the left side edge of the sleeve 31 passes to the recessed rear side of the arm |24, the latter is free to move to full ejecting position, moving the flange and liner correspondingly, as shown in Fig. 6.

Operation-In the use of the gun and load as described, the breech being open as in Fig. 3, the load in the form of a cartridge and liner as described is introduced into the breech of the gun and positioned as in Fig. 1, with the forward ends ofthe lands of the liner extended slightly into the bore 3| for support of the forward cartridge where it functions in a way corresponding vto end while the rear end of the liner rests on the ejector head 92. 'Ihe sleeve 31 and its supporting frame are then rocked to the left to the position of Fig. 4. It should be noted that in the rocking movement of the breech closure and supporting frame the arm is included, so that it is always against the head 38 of the chamber and breech closure. The handle 40 is then pushed forward, clearing it from between the lugs 46 and pressing the breech sleeve or chamber wall portion 31 forwardly against the base flange 11 of the rifling or liner and case member 16. The. operation is continued, the liner passing slidingly along the bore and being gradually pressed inwardly to a taper corresponding to that of the barrel. The flange 11 finally comes to rest against the shoulder 36, checking also further forward movement of the sleeve 31 in position for meshing of the interrupted threads thereon with those of the breech recess. The forward movement of the liner has thus carried the ejector head 92, rods 9| and 94 and arm 95 to their'forwardmost positions, shown in Fig. 2. Rotation of the chamber member as a breech closer, now, by movement of the handle 40 tothe lanyard 58 may be pulled to fire the chargeA in the cartouche. In the progress of combustion of the charge the projectile is moved forward from the position in Fig. 2 until the first flange 13 reaches the forcing cone at 33, and` is finally forced forward against the lands 80,

conventional construction as to engraving, sealing and rotating. As the ring 13 passes forward, it exerts sunicient pressure to intrude a part of the land material into the key grooves or recesses 83-85 as before indicated, instantly securing the lands against slippage on the face of the bore.

It is contemplated lthat the same liner may be used for several shots, l

After the firing of each shot the breech is opened by swinging the handle to the left to disengage the threads of the closure and tube, and the handle drawn back to position between the lugs 4D. his withdraws the riling-liner unit IB from the bore 3l by reason of the arm being pressed backward, drawing the rod 94 and the push rod 9| rearward so that the eX- tractor head 92 presses the flange 11 out closely following the end of the sleeve 3l. The latter having arrived -at its position clear of the breech as in Fig. 5, it may be swung to the right, clearing the anchor plunger from the head of the cartouche.

In the final opening movements of the sleeve 3'! and piston the ejector is caused to act, as before described, moving the liner to a position where it may be engaged by a hook or other tool for complete removal from the gun, together with the cartouche in which the preceding charge was red, if any parts of the cartouche remain.

In the event that the liner is to be continued in use for succeeding shots, it may be left in place. A new cartouche with projectile may be slipped into the used liner while still in place in the breech, and after positioning of the sleeve 31 against face i3d the new cartouche and old liner are pressed forward with the llange 'l1 against the extractor head 92, after which closing and ring of the gun are proceeded with as before described.

The small key grooving 83-85 or the like embodied as above will be largely protected from erosion and reduire retooling rarely, if at all during the life of the gun. It is an advantage that efficiency of the keying will not be materially affected by loss of exact contour in the grooves.

In the use of the chamber member herein disclosed, due to the time element involved in conduction of heat through the materials employed,

and the promptness to be expected in the openf ing of the breech after ring, a minimum communication of heat to the body of the tube is involved, and in addition a major increment of heat incident to firing of a given charge is dissipated by radiation and natural connection from the y chamber member, at a distance from the gun tube, which may be hastened by air circulating means known though forming no essential part of my invention.

Likewise, the withdrawal of the riing unit or liner immediately after each shot fired will, as in the case of the chamber member, though to a lesser extent, effect a removal from the bore of heat accreted in the liner, and enable its dissipation at a distance from the gun. My liner will also act in some degree as an insulator of heat for the tube, since the intimacy of its engagement with the bore is instantly lessened after passage of the rotating bands of the projectile.

While I have disclosed my invention with particularity in its best embodiment as far as developed, it will nevertheless be understood that modiiications of construction, arrangement, and combination of parts, substitution of material, and equivalents, mechanical and otherwise may i l0 be made without departing from the spirit of the invention set forth in the claims hereto appended, wherein I claim:

1. A gun and rifling consisting of a barrel having a main bore, a generally tubular inner land member longitudinally slidable therein and having spiral slots therein whereby the intervening material between the slots constitutes lands, said lands being of comparatively thin flexible material, the barrel having formed in the face of its bore and arranged to underlie said lands, shallow recesses adapted to receive portions of the lands therein by intrusion under pressure of sealing rings and anges lof projectiles in course of firing.

2. YThe combination of a barrel having a bore and a thin wall liner therefor having circumferentially spaced, helical slots completely through the wall thereof and extending along the major part of the barrel whereby the intervening material between each two slots constitutes a land,fthe

land'portions of said liner contacting the face of l said bore separably for longitudinal withdrawal at will and means to hold the liner releasably against relative rotation in the barrel during ring.

3. The structure of claim 2, said last-named means comprising a multiplicity of circumferential small recesses in the bore surface of said barrel and frictionally engaging the land portions of said liner during passage of a projectile along` said portions.

4. In combination with a gun, comprising a barrel having a bore enlarged at its breech end to form a chamber, a chamber sleeve tting said chamber and slidable `into and out of the chamber, and including means to releasably secure the sleeve in the chamber, a load including a cartridge case having a firing charge therein and a projectile in advance thereof, said case being of a diameter 'm fit said sleeve slidably, an outer barrel liner engaged exteriorly and slidably around said case and adapted to be slid into the bore of said barrel, said liner being constructed and arranged to be engaged by the forward end of the sleeve whenthe latter is moved into said chamber whereby the liner is projected into the bore said liner including a part held between the sleeve andA forward end of the chamber, means to hold said case in said chamber against forward movement with the liner, and means to lock and unlock the sleeve in the chamber.

5. The structure of claim 4, said part comprising a base ange of greater radius than the bore of said barrel, said flange being clamped between the inner end of said sleeve when the latter is in forward position and a shoulder between forward end of said chamber and the breech end of the bore.

6. The combination with a gun comprising a barrel having an enlarged breech chamber of a load comprising a cartridge case having a -iiring charge therein and a projectile in advance of the charge, an outer barrel liner engaged exteriorly and slidably around said case, and adapted to be moved slidably in the barrel into a forward position in advance of said chamber, and means to project the liner forwardly into the barrel from around the cartridge case, said means acting to secure the liner in said forward position.

'7. lA round of ammunition comprising in combination a case body shaped to t the chamber of a gun barrel, said case body shaped to hold a projectile, a projectile seated in said case body and projecting forwardly from the case body, said 11 projectile having an enlarged part deformable by a gun barrel when fired therethrough, conventional primer and propellent means in the case body, and a sleeve slidably tting the case body and extending forwardly thereof around said projectile beyond the enlarged deformable part, said sleeve being shaped to slidably t within the borevof a gun barrel in which the round is loaded.

8. In a gun, a barrel body having a bore, a separate rifling liner comprising a thin metallic member constructed to t smoothly within said bore, said liner having circumferentially-spaced helical slots through its wall, each pair of contiguous slots forming a land therebetween, the bore surface of said barrel having a plurality of helical, circumferentially-spaced grooves having a twist in a direction opposite to that of the slots in said liner said barrel grooves acting to engage and secure the lands of said liner in spaced parallel relation during passage of a projectile therealong.

9. In combination with a gun barrel having a bore and an enlarged breech chamber, a cartridge, a liner fitting about said cartridge and slidable forwardly thereof into said bore, means comprising a sleeve slidable into said chamber between said cartridge and the inner Wall of said chamber, said sleeve when slid into said chamber engaging said liner and projecting the same forwardly into said bore, and means for retaining said cartridge within said chamber when said liner is projected forwardly into said bore.

10. The combination recited in claim 9, said liner comprising a cylindrical shell having circumferentially-spaced helically-extending slots through the wall thereof, each pair. of adjacent' slots defining a land therebetween.

11. In a removable liner for an unrfled gun barrel, a cylindrical metallic shell having circumferentially-spaced, helically-extending slots therethrough, each slot beginning at a point spaced forwardly from the rear end of said shell and extending through the forward end thereof, said shell being shaped to fit the bore 'of the barrel.

12. A separable rifling liner for a substantially smooth bore gun tube, comprising a plurality of thin helically wound parallel circumferentiallyspaced bands, said bands being inter-connected at their rearward ends only by a throat portion integral with said'bands.

Y LEO MACKTA.

REFERENCES CITED The following references are of record in the file rof this patent:

UNITED STATES PATENTS Number VName Date 34,911 Swan Apr. 8, 1862 138,711l Taylor May 6, 1873 f 384,537 yNordenfelt June 12, 1888 446,807 Armit Feb. 17, 1891 631,399 Gillette Aug. 22, 1899 745,561 Bergersen Dec. 1, 1903 976,459 Hartmann Nov. 22, 1910 1,126,294 Saold Jan. 26, 1915 j 1,299,972 Linscott Apr. 8, 1919 1,321,883 Burns Nov. 18, 1919 1,343,444 Formby June 15, 1920 1,355,421 Pedersen Oct. 12, 1920 2,110,264 Gerlich Mar. 8, 1938 2,238,587 Gaidos Apr. 15, 1941 2,245,621 Summerbell June 17, 1941 2,359,517 Gebeau Oct. 3, 1944 FOREIGN PATENTS Number Country A Date 47,971 Germany Dec. 19, 1888 55,187 Germany Jan. 31, 1891 17,042 Great Britain 1897 Great Britain 1902 

